java - How can I write a function boolean succeeds(char a, char b, String s)? using s.equals(""), s.charAt(0), s.substring(1) -

i trying write function takes string s , returns true if every occurrence of character b succeeded character a, , false otherwise. have tried:

boolean succeeds(char a, char b, string s) {     boolean to_return = true;     boolean seen_a = false;     while(true) {         if (s.equals("")) return to_return;             char c2 = s.charat(0);             if (c2 == a) seen_a = true;             if (c2 == b) {                 if (!seen_a) return false;             }             s = s.substring(1);         }     } } 

i think have right idea. don't know how put together.

given guidelines, can along lines of

while (!s.equals("")) {     char c = s.charat(0);  // record first char     s = s.substring(1);    // cut off first char       // if "first char 'b' , next     // not 'a'", can return false     if (c == b && (s.equals("") || s.charat(0) != a))         return false;                 }  return true; 

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by way, can done more easily:

return s.replace(""+b+a, "").indexof(b) < 0; 

(i noticed approach outlined in @josephmyers' answer)